1. Field Of The Invention
This invention relates to an elastomeric oil seal which may be stretched during installation to a diameter substantially greater than its ultimate operational diameter and yet recover to serve as an effective and reliable oil seal.
2. Description Of Prior Developments
Although oil seals have been under development for many years, the design of seals for the rear end of an automotive crankshaft still poses several unique problems which heretofore have been left unsolved. One particularly bothersome design problem is caused by a radially extending flange projecting from the rear end of many conventional engine crankshafts. More particularly, the rear end of many crankshafts terminates in a flange which is much larger than the diameter of the inboard sealing position about which an oil seal is typically mounted. This arrangement can significantly complicate the installation of a seal around its inboard location. Since the flange is essential for connecting the power output end of the crankshaft to a flywheel and to a drive train leading to the rear wheels, it is necessary to design a seal which may be installed in a manner which accommodates the flange rather than to eliminate the flange from the crankshaft.
Rear crankshaft seals were originally constructed by wrapping a length of rope around the crankshaft at the rear sealing position and clamping the rope in place between the engine case and an extension of the rear bearing cap. This type of seal worked initially but its effectiveness was characteristically short lived and resulted in oily garage floors and oil slicks along the highways.
When elastomers were developed that could cope with the exotic additives and oils and high operating temperatures of modern automobiles, semicircular seals were molded in matched pairs and installed on opposing sides of the crankshaft during engine assembly. This improved the dependability of the seals over prior designs but presented another problem. The interfaces or contacting surfaces between the two seal halves often did not fit properly or wore unevenly and resulted in oil leakage, often after only a few miles of operation.
During a subsequent period of seal development which has lasted for at least the last twenty years, automobile manufacturers have been searching for some type of one-piece oil seal that could be used reliably in the rear crank position. Until the present invention, engineers have been trying to develop such a one-piece seal without notable success.
Some prior sealing device structures include U.S. Pat. No. 2,523,604 which discloses a rear crankshaft oil seal somewhat similar to the present invention. However, this seal is split to enable the seal to encircle the crankshaft. This split can easily create a leakage path from the sealed fluid to the environment. In contrast, the present invention provides a continuous unbroken sealing member which is stretched over the flange and relies on elastomeric memory for recovery into its sealing configuration.
U.S. Pat. No. 4,145,057 shows a complete circular sealing element for use as a packing between a cylinder and a piston where the relative motion between the piston and seal is axial. In this configuration no flange is present which has a diameter greater than the diameter of the piston over which the packing must be stretched. Further, the packing has no feature that would prevent rotational movement between either of the sealed members and the packing. In the present invention, the centrifugal force of the sealed fluid requires the external periphery of the seal to form a static seal with the encircling bore.